The present invention relates to a digitizer and stylus pen unit, and relates more particularly to a wireless digitizer and stylus pen unit.
Regular digitizer and stylus pen units are divided into four groups, namely, the battery added digitizer and stylus pen units, the rechargeable wireless digitizer and stylus pen units, the LC resonance type digitizer and stylus pen units, and the infrared induction type digitizer and stylus pen units. A battery added digitizer and stylus pen unit is not convenient in use because the stylus pen is huge and the wireless digitizer and stylus pen unit is also not convenient in use because the battery must be regularly charged. Furthermore, the battery added digitizer and stylus pen units and the rechargeable wireless digitizer and stylus pen units tend to produce an error action when the voltage level of the battery is weak. The drawback of LC resonance type digitizer and stylus pen units is that the out put signal of the stylus pen is a modulated signal which tends to be interfered by external radio waves. Infrared induction type digitizer and stylus pen units are also not satisfactory in function because of the limitation of infrared induction. Because the digitizer of an infrared induction type digitizer and stylus pen unit has a dead angle on the induction of infrared rays, and induction failure tends to occur during the operation of the unit. This problem is more apparent on a big scale infrared induction type digitizer and stylus pen unit.
The present invention has been accomplished to provide a wireless digitizer and stylus pen unit which eliminates the aforesaid drawbacks. According to one aspect of the present invention, winding type conductor loop is provided to act with the stylus pen through the change of a magnetic field, and therefore the problems of the installation of an added battery and the performance of charging a rechargeable battery are eliminated. According to another aspect of the present invention, the induction between the winding type conductor loop and the stylus pen is the change of a magnetic field but not the change of a frequency, therefore the induction is free from the interference of external radio waves and does not interfere with other computer peripheral equipment. According to still another aspect of the present invention, a voltage level hold circuit is operated with an A/D converter and a data buffer to provide the central processing unit with Z-axis coordinate value, and therefore three-dimensional character and graphic designs can be achieved by means of the changes on Z-axis, Y-axis, and Z-axis.